Field of the Disclosure
The present disclosure relates generally to wireless multicast transmissions, and more specifically to increasing the rate of successfully received Wi-Fi or WLAN multicast packets to client devices that have a listen interval exceeding a DTIM interval.
Description of Related Art
Multicast over a wireless network (e.g., Wi-Fi or a wireless local access network (WLAN)) is group communication where a wireless access point (or “AP”) sends frames destined for a group of clients (also known as “listening stations” or “destination computers”) simultaneously. Unicast over a wireless network is communication where the wireless access point sends frames to a particular client. Beacons or beacon frames are periodically transmitted by the access point to announce the presence of a wireless local access network (or “wireless LAN” or WLAN). Beacons can include information indicating to clients that data is being temporarily stored or buffered on the access point and is ready for transmission to a given client (for unicast transmissions) or to a group of clients (for multicast transmission) (e.g., TIMs or DTIMs). Clients often enter sleep modes in order to conserver power, and select a listen interval or sleep interval that determines how often they wake up to listen for multicast traffic. For unicast data buffered at the access point, a traffic indication map (or “TIM”) is sent with each beacon to indicate to sleeping clients that buffered data at the access point is waiting for unicast transmission to the sleeping client. For multicast data buffered at the access point, a delivery traffic indication message (or “DTIM”) can be periodically sent with beacons, and indicates whether multicast frames are to be delivered in the upcoming beacon interval. A DTIM can have a lower periodicity than the TIMs (e.g., with every beacon, with every second beacon, with every third beacon, etc.). A DTIM interval indicates the periodicity of the DTIMs and is a parameter of the wireless network (e.g., Wi-Fi or WLAN to name two) and often selected by the access point. An access point may select a DTIM interval based on a tradeoff between latency, buffer size requirements, and power saving. Similarly, a client may select a sleep interval based on a tradeoff between latency, buffer size requirements, and power saving. When buffered data at the access point is waiting for multicast transmission, the next DTIM includes an indication that the multicast data is about to be transmitted. Once the DTIM indicates multicast data is ready for transmission, the access point expects all sleeping clients to awake and listen for the multicast.